Alpha-numeric information from a user of an electronic device is conventionally entered using a digital keypad or keyboard. Handheld devices, such as cellular telephones already have limited space for a keypad. As the functionality of handheld devices increases, the space constraint is made more severe by the use of larger display screens. Handheld devices tend to have bigger display screens for increased viewing pleasure while maintaining the same palm-size form factor for good portability. As a result, the space taken up by operational tools tends to be reduced to accommodate the larger display screen. This trend is evidenced in the contemporary design of cellular phones, where the space for keypad and buttons has been reduced significantly to make room for the increasingly bigger display screen. For handheld devices with a touch sensitive screen, most operations have moved to the display area where they are accessed through software, hence, there are not many hardware control components left on the device body. However, the majority of handheld devices in the marketplace still tend to have non-touch-sensitive screens for cost, durability, power saving and various reasons. On these types of devices, operations are inevitably done through hardware components. Thus, they have to take up space on the device body. Therefore, the designer is faced with the challenge of making the operation tools as small as possible while still keeping the versatility of those tools.
There is a limit to how much the space for operational usage can be reduced. If the space becomes too tiny, it would make the thumb and finger operation difficult, if not entirely impossible. On the other hand, the designer cannot sacrifice the versatility of operational tools only for the sake of making it comfortable to use. All of the operational functions must be retained, no matter how much the size of the tools is reduced.
Most basic operations on handheld devices fall into three main categories: navigation and control, text input and phone dialing.
For navigation and control functions, the conventional 4-direction navigation method has been widely used. Some implementations are done using a dedicated 4-directional button, like Motorola's Timeport P935 Personal Interactive Communicator (PIC or 2-way pager); others use a combination of navigation roller and button, like Nokia's 7110 series of cellular phone; while others are implemented on keys, like Motorola's Timeport P8767 cellular phone. In addition, a data entry device is disclosed in U.S. patent application Ser. No. 09/4655789, “Chart Navigation Using Compact Input Devices”, filed Dec. 17, 1999.
For text input, most handheld devices depend on the standard keypad, like Motorola's iTAP text input system on V8088 cellular phones, others use a shrunk version of the QWERTY keyboard, like Motorola's Timeport P935 PIC, often accompanied by other auxiliary buttons or keys. There exist various designs of text input devices employing a set of 8 or 9 keys. These keys can be a subset of the keys on a standard keypad or can be a separate set of dedicated keys or buttons. In addition, a data entry device is disclosed in co-pending U.S. patent application Ser. No. 09/317,518, “Data Entry Device Recording Input in Two Dimensions”, filed May 24, 1999.
Prevailing methods for phone dialing rely on the standard keypad for phone number entering. There exist other designs employing special control mechanisms for phone number entering as well as for text input. However, none of the methods mentioned above provide an integrated solution to meet user's need of one set of keys or tools for all 3 major operational functions. In other words, for each individual function, a user has to select a separate set of control keys or tools to perform the task. This way of operation requires a larger space on the device than would otherwise be comfortable for normal thumb-and-finger operation.